"Some cattle harbor E. coli O157:H7 and other disease-causing bacteria,
and these pathogens can persist in manure for long periods of time," said
Agricultural Research Service
microbiologist James B. Russell. "But in lab studies, adding sodium
carbonate kills many of these harmful microbes." ARS is the chief research
agency of USDA.

Russell works at the ARS U.S.
Plant, Soil and Nutrition Laboratory in Ithaca, N.Y., and is affiliated
with the Nutrient Conservation and Metabolism Laboratory at Beltsville, Md.
Russell collaborated with postdoctoral fellows Francisco Diez-Gonzalez and
Graeme Jarvis, and with undergraduate student David Adamovich in Cornell's
Department of
Microbiology on the research.

Russell's team had been looking for a practical and inexpensive method for
treating dairy cattle manure to decrease E. coli O157:H7 and other potential
pathogens.

"Bacteria can be killed by chlorination, but chlorinating manure is not
practical," Russell said. "Laboratory tests indicated that E. coli
was resistant to alkaline pH and ammonia, but it was very sensitive to
carbonate if the pH was alkaline."

Carbonate can be derived from urine. "When urease--an enzyme in feces--
breaks down urinary urea, some carbon dioxide is trapped as carbonate. Urinary
carbonate alone can kill E. coli, but cows don't make enough urine to kill all
the E. coli," Russell said. The ARS-Cornell team made its discovery by
mixing manure and urine. When the ratio was 1-to-1, virtually all of the E.
coli were killed. However, dairy cows typically excrete 2.2 times as much feces
as urine, and E. coli persisted at that ratio.

"If cow manure samples are spiked with sodium carbonate in the
laboratory, E. coli do not persist," Russell said. Some sodium hydroxide
is also added to make sure that the pH is at least 8.5, but "the estimated
cost of this treatment would be only $10 per dairy cow per year," he said.

Russell indicated that "after only 5 days, the E. coli count was less
than 10 cells per gram." Because the manure samples originally had from
100,000 to 100,000,000 counts per gram, "carbonate appears to be an
extremely effective antibacterial agent," Russell added.

Cattle manure is often stored outdoors in large tanks or ponds prior to
spreading on fields, but "a threefold dilution with water did not diminish
the effectiveness of carbonate treatment," Russell said.

While this process looks very promising in the laboratory, "pilot and
farm-scale testing will be needed before the technology can be recommended to
the livestock industry," he added.

Laboratory experiments also indicated that carbonate killed other bacterial
pathogens such as Salmonella typhimurium, Streptococcus pyogenes, Klebsiella
pneumoniae, and Staphylococcus aureus. This research is reported in volume 34,
issue 7 of Environmental Science and
Technology.